After 10 years of planning and three years of site preparation, it took less than a minute Sunday for workers to scrape a hole in a levee and begin the renewal of 1,000 acres of former North Bay marshlands.

The mechanical excavator scooped aside a few buckets of dirt. Muddy water spurted and then flowed into the waiting basin. Now all that’s needed is time.

“We’re talking 20, 30 years,” said Julian Meisler, baylands program manager for the Sonoma Land Trust, which purchased the land in 2005. “Bringing a marsh to life is a major effort.”

That effort was celebrated Sunday at Sears Point Ranch, south of Highway 37 and west of the well-known Sonoma Raceway. There was a circus-scale white tent, sparkling-wine mimosas and individual quiches for several hundred people — some of them contributors to the $18 million fundraising effort led by the trust, some of them government officials who steered grants to the project.

“We’re going to see more wildlife, more waterfowl, more endangered and threatened species” on this portion of the shoreline between Mare Island and the Petaluma River, said Rep Mike Thompson, D-St. Helena. “This area is going to live on for future generations.”

First, though, the 1,000 or so acres need to come to life.

The ranch is the latest foray in an ongoing campaign to restore the buffer zone of tidal marshes that once encircled San Francisco Bay. There are the ecological benefits that Thompson noted; there’s also the value of marshland as buffer against the rising sea levels projected for coming decades, a gradual expansion of the bay that will be exacerbated during super-high tides or during strong storms.

New terrain sculpted

The sooner that bay marshes are restored, scientists say, the sooner they can put down roots and adapt to the shifting conditions. But it’s not simply a matter of piercing a levee and letting nature take over.

Off and on for three years leading up to Sunday’s ceremony, construction crews from Magnus Pacific shaped a new terrain behind the levees of rocks and dirt that once protected fields of grain planted in the late 19th century to feed the region’s growing population. A new levee toward the north edge of the property was formed that not only will keep high tides away from Highway 37, it has a broad slope toward the bay that will provide upland habitat to wildlife.

Behind the old and new levees, meanwhile, parched farmland was pushed into a bumpy landscape of what are called “marsh mounds” — undulations that will accelerate the buildup of sediment that flows in during high tides, helping the marshlands take shape a decade or so more rapidly than what otherwise might be the case.

“We’re relying on the natural tides to build this, so we want to get as much of the sediment as we can,” Meisler said. In all, the equivalent of 6 miles of channels were excavated and rearranged to form the levee and the mounds.

2nd breach to come

Within 15 minutes of the initial breach, a 285-foot-wide gap in the levee churned with water and silt, the land behind filling in more by the moment. Another breach will occur in the next week on the east end of the site; by next summer there will be a new 2.5-mile stretch of the Bay Trail atop the levee, along with such recreational amenities as a kayak launch.

This is the latest in a series of ranchland reclamations that in the past generation have created nearly 15,000 acres of marshes between Petaluma and Vallejo. More than 5,000 acres are waiting to be restored, and the trust has an additional 4,000 acres on its wish list.

Support of tribe

Before the crowd walked a mile to watch the levee break, the final speaker was Greg Sarris, tribal chairman of what is now the Federated Indians of Graton Rancheria. The tribe in 2002 put a down payment on the ranch with plans for a casino; instead, it donated its $4 million option to the trust and shifted its attention north to Rohnert Park, where the casino opened in 2013.

“This was an opportunity for all of us to work, Indians and non-Indians alike, to take care of the land,” Sarris said. “We’ve always understood that the health of the water is linked to the health of the people.”

John King is The San Francisco Chronicle’s urban design critic, taking stock of everything from Salesforce Tower to public spaces and homeless navigation centers. A two-time Pulitzer Prize finalist and author of two books on San Francisco architecture, King joined The Chronicle in 1992 and covered City Hall before creating his current post in 2001. He spent the spring of 2018 as a Mellon Fellow in Urban Landscape Studies at Dumbarton Oaks in Washington, D.C.